Several methods have conventionally been proposed to improve the firmness and elasticity of keratinous fibers such as hair, wool and other keratinous fibers for knitting or weaving. The following 1) to 4) may be mentioned as examples of such methods:
1) Polymers incorporated into a perming liquid or a hair dye composition are adsorbed onto the surface of the keratinous fiber (Japanese patent publication "Kokai" Nos. 52-7449 and 58-216113), PA1 2) Protein hydrolysates are permeated into the keratinous fiber, PA1 3) The keratinous fiber is shrinked by a shrinking agent (Japanese patent publication "Kokai" Nos. 55-108812, 58-109405 and 60-87208), and PA1 4) A water-soluble substance is contacted with a keratinous fiber to form a water-insoluble or sparingly soluble salt inside the fiber (Japanese patent publication "Kokai" No. 1-233208). PA1 (A) A first agent containing a metal ion, PA1 (B) A second agent comprising:
However, these methods are not necessarily successful. In method 1) above, when the keratinous fibers are shampooed, the firmness and elasticity imparted to the fibers will easily be lost, because the polymers which had been adsorbed onto the surface of the fibers are washed away. In method 2) above, sufficient effect cannot be obtained because the protein hydrolysates to be used generally have molecular weights over several thousands, and this means that only a slight amount of protein hydrolysates can be permeated into the keratinous fiber. In method 3), metal ions are generally used as a shrinking agent. The shrinking effect is obtained from a chelating reaction between the metal ion and a functional group (mainly a carboxyl group) in the keratinous fiber. Therefore, when the keratinous fiber is shampooed with an ordinary shampoo which contains a chelating agent such as sodium ethylenediaminetetraacetate, a chelate exchanging reaction takes place, which causes a gradual extinguishment of the shrinking effect. Method 4) is good in that a certain degree of firmness and elasticity can be imparted, and they can last after the fibers undergo several shampooing. However, when the concentration of the active ingredients is raised with an aim to improve the effect, considerable amounts of water-insoluble or sparingly soluble salts deposit on the surface of the hair fiber, causing objectionable frictional and rough feeling of the hair.
Accordingly, compositions for treating keratinous fibers which can provide the fibers with excellent firmness and elasticity while avoiding objectionable frictional or rough feeling to the touch have still been desired.